Monatin is a high-intensity sweetener having the chemical formula:

Monatin includes two chiral centers leading to four potential stereoisomeric configurations. The R,R configuration (the “R,R stereoisomer” or “R,R monatin”); the S,S configuration (the “S,S stereoisomer” or “S,S monatin”); the R,S configuration (the “R,S stereoisomer” or “R,S monatin”); and the S,R configuration (the “S,R stereoisomer” or “S,R monatin”). As used herein, unless stated otherwise, the term “monatin” is used to refer to compositions including all four stereoisomers of monatin, compositions including any combination of monatin stereoisomers, (such as a composition including only the R,R and S,S, stereoisomers of monatin), as well as a single isomeric form.
For purposes of this disclosure, the monatin carbon backbone will be numbered as illustrated above, with the carbon directly covalently attached to the alcohol group being identified as the 2-position carbon and the carbon directly covalently attached to the amino group being identified as the 4-position carbon. Consequently, references herein to R,R monatin, S,S monatin, R,S monatin, and S,R monatin mean: 2R,4R monatin, 2S,4S monatin, 2R,4S monatin, and 2S,4R monatin, respectively, unless otherwise indicated.
It should be noted that in the literature, the monatin carbon backbone has also been numbered using an alternative convention, with the carbon attached to the alcohol group being the 4-position carbon, and the carbon attached to the amino group being the 2-position carbon. Accordingly, for example, references to 2S,4R monatin in this disclosure would be the same as references to 2R,4S monatin in literature using the alternative numbering convention.
Furthermore, because of various naming conventions, monatin is known by a number of alternative chemical names, including: 2-hydroxy-2-(indol-3-ylmethyl)-4-aminoglutaric acid; 4-amino-2-hydroxy-2-(1H-indol-3-ylmethyl)-pentanedioic acid; 4-hydroxy-4-(3-indolylmethyl)glutamic acid; and, 3-(1-amino-1,3-dicarboxy-3-hydroxy-but-4-yl)indole.
Certain isomeric forms of monatin can be found in the bark of roots of the Schlerochiton ilicifolius plant located in the Transvaal Region of South Africa. U.S. patent application Ser. Nos. 10/422,366 (“the '366 application”) and 10/979,821 (“the '821 application”), which are hereby incorporated by reference, disclose, inter alia, polypeptides, pathways, and microorganisms for in vitro and in vivo production of monatin.